Chromatin Topological Transitions

(Received February 24, 2011)DNA transaction events occurring during a cell cycle (transcription, repair, replication)are always associated with severe topological constraints on the double helix. However, sincenuclear DNA is bound to various proteins (including histones) that control its accessibilityand 3D organization, these topological constraints propagate or accumulate on a chromatinsubstrate. This paper focuses on chromatin ber response to physiological mechanical con-straints expected to occur during transcription elongation. We will show in particular howrecent single molecule techniques help us to understand how chromatin conformational dy-namics could manage harsh DNA supercoiling changes.